Process for electrochemically producing stable images and characters



Patented Aug. 21, 1934 t 1,970,539

PROCESS FOR ELECTROCHEDIIOALLY PRO- STABLE IMAGES AND CHABAC- Viktor Banach, Jr., Berlin, Germany No Drawing. Application February 16, 1932, Serial No. 593,428. In Germany February 21, 1931 24 Claims. (Cl. 204-1) It is known to produce hara t r lectrointo question either all tend to autoxidize or else chemically by bringing a Paper saturated with the coloured reaction products produced are unthe solution of an electrolyte between electrodes, stable. As a result, either t paper Which has a coloured material being produced at the points ot yet been passed th ou the wr n a paat which the electric current passes. ratus is not stable in the prepared condition or 60 The coloured substance which forms the charlse h chara r produced disappear again acters may be produced firstly from the decomafter a time, or a a n th places of the image p i ion products of the electrolyte, e. g. from which ought to remain white colour over after a potassium iodide, secondly by the action of the time.

to ions activated by the electrolysis on a reagent In parti ula the Organic bodies which react 65 present in the paper, e. g. production of th blu in a secondary reaction with cations or anions colour by kathodic treatment of thymolphthalein, activated from the C u g electrolyte y the thirdly by anodic oxidation of leuco bases to their lec rolysis either alone in Presence of a corresponding dyestuffs, e. g. anodic oxidation ther reagent which promotes the production of it; (tetramethyl-p-diamino triphenylmethane to dyestuff, with formation of a sufiiciently stable to malachite green), fourthly by producing organic colouring material, all have the disadvantageous metal compounds by means of a soluble metal property of colouring in the atmosphere, so that electrode from which metal ions are discharged the white places of the image become so dark during the passage of current, said ions forming a after a short time that the picture or the writing coloured compound or a lake with a suitable can no longer be recognized. In the converse case 75 organic substance, flfthly by kathodic reduction the electrochemically produced colouring mateof salts which form hydrogen sulphide and secrial of the characters or images, is unstable so ondary production of coloured metal sulphides. that after a short time the said characters or All these known process have substantial disimages bleach out, particularly in the light, the

advantages. The iodine marks, very precise and white places of the image naturally being re- 3 produced by means of very low current strengths, tained. Practically only those agents come into are not absolutely stable owing to the high vapour consideration, therefore, the primary or secondpressure of iodine. In addition, the high price of ary electrolytically produced decomposition prodiodine compounds imposes narrow limits upon ucts of which comprise stable dyestuffs or the economical use ofthese substances. colouring materials.

When soluble electrodes are used, which, it is The practical use of such agents, however, true, produce stable marks or images, there is necessitates the elimination of spontaneous subthe substantial disadvantage that the electrode, sequent colouring of the white places of the more particularly the anode, is so much attacked image by the action of the atmosphere of the 35 in a very short time that it must be replaced, so light. 9 that continuous working, more particularly on According to the present invention this is pro= the so-called tape writing machines is impossible. duced by changing, eliminating or removing from The secondary production of coloured metal sulthe image support one or several colour-forming phides by the primary kathodic reduction of agents, directly or only a short time after the salts which form hydrogen sulphide cannot come passage through the electrodes or directly or 95 into consideration when only small current a short time after the image has been made, in strengths are available or a very high speed of such a way that the possibility of further forwriting is required, such as for example, in picmation of colour or dyestuff, either by interior ture telegraphy, since this reaction requires a or exterior influences, is excluded.

y h h electrical u p n acco nt f its siug- This action, which corresponds somewhat to 1m gishness. the fixing of a photographic plate, could be Those processes which depend on the producbrought about by means of a chemical aftertion of coloured reaction products by anodic oxitreatment. Such an after-treatment, however, dation of more particularly organic bodies or is very difficult to carry out practically and in by the secondary reaction of organic agents with the case of many telegraphic apparatus can- 1 5 the cations or anions activated from a conductnot be carried out at all. ing electrolyte by electrolysis certainly have the Preferably the removal of one or several of advantage of the insoluble electrodes, but on the colour-farming agents or else the renderthe other hand they also have the substantial ing of the same innocuous as regards further fordisadvantage that the organic agents which come matiou Q colou is eiiected by using for the 1m colour-forming agent such a body or such bodies which volatilize during the drying of the image support which is always to be written on whilst moist.

It is known electrochemically to produce images by anodic oxidation, for example, of aromatic amines. If, instead of the solid aromatic amines hitherto used, an amine is chosen which volatilizes during the drying of the image support, which, however, can be oxidized very readily to a very stable dyestufi or colouring material, then no further colouring can occur in the white places of the image by subsequent autoxidation of the amine since this isno longer present, and the image is to a certain extent fixed.

In place of the anodic oxidation of a suitable volatile amine other volatile bodies may also be used as the colour-forming agent whch show this characteristic. Preferably only such bodies are used which volatilize more slowly than water.

For example, volatile hydroxy-benzenes or hydroxy-napthalenes, or derivatives thereof, inasmuch as they are sufficiently volatile, come into consideration, either alone or together with another organic or inorganic agent with which they further react to form a colouror dye, preferably in an alkaline medium, which is formed by the electrolytically activated cations from the neutral or slightly acid conducting electrolyte. This process also has the advantage that when writing kathodically the electrode which does the writing need not consist of noble metal. The

employment of volatile substances as colour.

forming bodies comes more particularly into consideration for the continuously operating socalled tape writers which are fed with moist rolls of electro-chemically sensitive paper. The volatile agent is very well excluded from air and light in the moist rolls. Since the moist rolls must be stored in such a way that the moisture the image support soon dries, the unreacted colour-forming agent volatilizing at the same time.

According to the foregoing description the action of the atmosphere is to be used as the means for fixing the marks produced, 1. e. the heat of the room, the sensitive colour-forming agent being expelled from the image support by volatilization. Light can also be used in a similar manner as the fixing agent. According to the invention in this case those bodies are to be used as colour-forming agent which have the property of reacting by ordinary electrochemical attack, directly or indirectly, e. g. by way of a conducting electrolyte, alone or in combination with another body, with formation of colour, and which lose this property as soon as they have been exposed to the light.

These properties are shown, for example, by the light sensitive diazo-compounds (Liesegangs photographisches Archiv 1891, page 143; Eders Jahrbuch 1892, page 458; Pliotographische Korrespondenz 1895; Ber. 1902, Teil 34, p. 1668;

.Plotnikow, Lehrbuch der allgemeinen Photochemie, 1920, p. 540 ff).

4 Such diazo-compounds are. extraordinarily stable in neutral or weakly acid media provided they are kept away from the influence of light; on the other hand they are so sensitive as well that by a small displacement of the hydrogen ion concentration of the surrounding medium towards the alkali side they instantly enter into combination with themselves or with a phenol present or one of the known azo components with the formation of extremely stable azo dyestuff. If now such diazo-compounds which are sensitive to light, 1. e. are decomposed by light, are used as colour-forming bodies in the image support, then the sensitivity in all the white places of the image is completely removed as soon as the completed image has been exposed for a short time to a natural or artificial source of light. Light sensitive diazo-compounds come into consideration which unite with an azo component in alkaline medium which is applied from the first or incorporated with the image support together with the diazo compound and the conducting electrolyte, or else is added only immediately before the passage through the electrodes, or which combines with itself to form a dyestufi without any such components.

The process is not limited to the employment of diazo compounds. Other organic or inorganic bodies may be used which may be capable of forming dyestufi inasmuch as they lose this capability of responding to the light or other action.

Examples 1. Absorbent paper is thoroughly saturated with an aqueous solution of 10 parts by weight of potassium chlorate and 10 parts. by weight of potassium chloride in which 3 parts by weight of o-toluidine are dispersed. The paper is then "anodically written. Dark characters are obtained on a bright background. During the drying of the moist paper the colour-forming o-toluidine volatilizes so that even after the passage of time the white places of the image remain white.

2. Absorbent paper is thoroughly moistened with an aqueous solution of 20 parts by weight of sodium chloride and 3 parts by weight of po-- tassium ferricyanide in which 2 parts by weight of acetyl resorcin are dispersed. The paper is written on by means of the kathode and owing to the free alkali formed electrolytically as a result of the passage of current the resorcin combines with the ferricyanide with the formation of a dark brown colouring matter. When the paper is dried the acetyl resorcin which is the colour-forming body proper volatilizes with the water. The residue of ferricyanide, which merely imparts to the image a slightly yellowish ground colour, may remain in the image support without any danger to the stability of the written image.

3. Absorbent paper is thoroughly saturated with an aqueous solution of 10 parts by weight of ammonium chloride and 2 parts by weight of diazotized p-amidodiphenyl-amine, to which 10 parts by weight of a 1% alcoholic solution of resorcin have been added. The paper is written on kathodically. The ammonia electrolytically liberated at the kathode during the passage of current instantly brings about the combination of the diazo-compound with the phenol, with production of a brown insoluble dyestufi. The still moist image is exposed to a powerful source of light as a result of which the diazo-compound is so changed with accompanying loss of its yellow colour that it loses the capability of combining with the phenol. In this way sharp dark brown marks are obtained on a white background. The danger of subsequent colouring over of the white parts of the image is excluded.

What I claim is: g

1. A process for the electrochemical production lid ill]

of stable images or characters, more particularly tor the recording 01' telegraphically transmitted pictures, in which the characters are formed by an electric current on a support provided with a substance selected from the group: volatile hydroiwbenzenes and derivatives thereof, volatile hydrorynaphthalenes and derivatives thereoi, volatile aromatic amines, and light-sensitive disco-compounds oi the p-amino-diphenylamine type, together with a compound which reacts with the selected substance to produce a coloured product under the influence oi the current, and the recorded characters are fired by stabilizing the uninfiuenced portion oi the support.

2. A process for the electrochemical production of stable images or characters, more particularlp tor the recording of telesraphically transmitted pictures, in which the characters are termed byan electric current on a support provided with a substance selected from the group: volatile hydrox" ybenzenes and derivatives thereof, volatile hydrouynaphthalenes and derivatives thereof, volatile aromatic amines, and liaht sensitive dissoccmpounds of the p-amino-diphenylamine type, together with a compound which reacts with the selected substance to produce a coloured product under the influence oi the current and an electrolyte for promoting conduction of the current through the support, and the characters are fined by stabilizing the uninfluenced portion or the support.

3. A process for the electrochemical production oi stable images or characters, more particularly for the recording oi telesraphically transmitted pictures, in which the characters are formed by an electric current on a support provided with a substance selected from the group: volatile hydronybenzenes and derivatives thereof, volatile hydroiiynaphthalenes and derivatives thereoi, and volatile aromatic amines, together with a compound which reacts with the selected substance to produce a coloured product under the in iluence oi the passage of the current, and the characters are fixed by removing from the sup-=- port the unchanged substance selected from the aforesaid group by evaporation thereof.

A process for the electrochemical. production of stable images or characters, more particular ly for the recording of telegraphically transmitted pictures, in which the characters are formed by an electric current on a support provided with a lluht-sensitive diam-compound of the p-aminodiphenylamlne type together with a compound which reacts therewith under the influence of the current to form a coloured product, and the recorded characters are fired by exposing the support to light, whereby the unreacted discocompound is decomposed.

5. A process for the electrochemical production of stable images or characters, more particularly for the recording of telegraphically transmitted pictures, in which the characters are formed by an electric current on a support provided with a light sensitive diazo-compound of the p-aminodiphenylamine type of an sac-component, the former compound reacting with the latter under the influence of the current to form a coloured product, and the recorded characters are fixed by exposing the support to light, whereby the unreacted diam-compound is decomposed.

d. A process as claimed in claim 5 in which the support is also provided with alkali halide to promote conduction of the current.

7. A process for the electrochemical production of stable images or characters, more particularly 3 for the recording of telegraphically transmitted pictures, in which the characters are formed by an electric current on a moist support provided with otoluidine and an oxidizing agent, the iormer compound being oxidized by the latter to a dark product under the action of the electric current, and the image is fixed by drying the moist support, during which operation the unchanged o-toluidlne volatilizes.

s. A process for the electrochemical production oi stable images or characters, more particularly for the recordina oi telegraphically transmitted pictures, in which the characters are formed by an electric current on a moist support provided with o-toluidine and potassi chlorate, the former compound being oxidized by the latter to a clarlr product under the action or the electric current, and the image is fixed by drying the moist support, during which operation the unchance o toluiciine voletilizes.

s. A process as claimed in claim 8 in which the support is also provided with allzali halide to promote conduction oi the current.

it. A process for the electrochemical production oi stable images or characters, more particularly for the recording of telegraphically transmltted pictures, in which the characters are formed by an electric current on a moist support provided with acetyl resorcin and potassium rerricyenide, which interact under the influence oi the electric current with formation oi as darlr product, and the image is lined by drying the moist support, during which operation the unchanged acetyi resorcin volatilize-s.

ii. A process as claimed in claim is in which the support is also provided with alkali halide to promote conduction of the current.

12. For use in the electrochemical production oi stable images or characters, more particularly for the recording of telesraphically transmitted pictures, a support consisting of a material selected from the group consisting oi? paper, fabric and cellulose hydrate film, provided with a substance selected from the group: volatile hydrorybenzenes and derivatives thereof, volatile hydrcxynaphthalenes and derivatives thereof, volatile aromatic amines, and light-sensitive diam-compounds of the p-amino-diphenylamine type, together with a compound which reacts with the selected substance to produce a coloured productunder the influence of the current.

13. For use in the electrochemical production of stable images or characters, more particularly for the recording oi telegraphically transmitted pictures, a support consisting of a material u selected from the group consisting of paper, fabric and cellulose hydrate film provided with o-toluidine and potassium chlorate.

it. For use in the electrochemical production of stable images or characters, more particularly for the recording of telegraphically transmitted pictures, a support consisting of a material selected from the group consisting oi paper, fabric and cellulose hydrate film provided with o-toluidine and potassium chlorate, and an alkali halide to promote conduction of the current.

15. For use in the electrochemical production of stable images or characters, more particularly for the recording of telegraphically transmitted pictures, a support consisting of a material selected from the group consisting of paper, fabric and cellulose hydrate film provided with a light-sensitive diazo-eompound of the p-aminodiphenylamine type and an use-component.

16. For use in the electrochemical production lllil or. stable images or characters; more-particularly for the recording or telegraphically transmitted pictures, asupport consisting" -'ot' a' materialselected from the group consisting of paper,-

fabric and cellulose hydrate-film provided "with a light-sensitive diam-compound of the p-amino diphenylamine type and arr az'o component, and annalkali halide to promote-conduction' ot the current. l 17; For use-in the electrochemical production of stable images or characters, more particularly for the recording of telegraphically transmitted pictures, a support consisting" ct a --.materi'al't selec'tedfrom thegroupconslsting otpaper fabric and cellulose hydrate film provided with acetyl" resorcin and potassium ferricyanide.

18. For use in the electrochemical"production of stable images or characters, more particularly for the'recordin'g: of telegraphically transmitted" a background carrying bodies 'capable oi forming stable coloured substances under the influence of the electriccurrent and thereupon stabilizing the influenced part of the background, thereby preventing'iurtherformation of coloured substances 20. A process for the -electrochemical production of stable images'orcharacters, more particularly for the purpose of telegraphic transmission of pictures, which consists in producing images or characters by-an electric current on a background carrying, in addition to a conductingelectrolyte, bodies capable oil forming stable coloured substances under the influence of the electric current and thereupon stabilizing the uninfiuenced part or the background, thereby preventing further formation of "coloured substances. 1

21. A process" tor the electrochemical production 'ofstableimages orcharacters, more particularly' for' the purpose of telegraphic transmission-of pictures, whichconsists'in producing images-or characters by tin-electric current'on a" background carrying volatile bodies- --capabl'e 01 forming stable coloured substances linden-the: influence of the electric current and thereupon stabilizing H the-:uninfluenced part of the back ground by-evaporation or the uninfluenced-vol'a tile bodies-contained in the background, therebypreventing i'urther formation of coloured substances. a 22. A process for the electrochemical product tion of stable images or characters, more pai ticularlyi'or the purpose of telegraphic trans? mission of pictures, which consists in producing images or characters by an electric current oria -backgroundcarrying water volatile bodies capable 01 forming stable coloured substances der' the influence of the electric current and thereupon stabilizing the images or characters. by evaporation of the uniniluenced water volatile I bodies contained in the background, thereby pre--' venting further formation of coloured sub--' stances. 23. A process for the electrochemical production of stable images or characters, more per-- ticularly for the purpose of telegraphic trans- 101' mission of pictures, which consists in producing images or characters by an electric current on ail-f background carrying bodies capable of forming stable coloured substances under the influence of the electric current and adapted to losein the 5 coloured substances under theinfiuence of the- 'electric current and adapted to lose in the light 12c and thereupon stabilizing the uninfiuenced part their capability of forming coloured substances,

of the background by exposure to light, thereby preventing further formation of coloured substances.

' VIKTOR BAUSCH, JUN.

rec 

